1. Field of the Invention
This invention relates to an image forming apparatus possessing an ability to inscribe a date and more particularly to an image forming apparatus adapted to permit changes in the date to be inscribed.
2. Description of the Prior Art
The image forming apparatus such as a copying machine or a printer using the electrophotographic process is provided with a photosensitive drum and, therefore, is allowed to form an electrostatic latent image on the surface of the drum by electrically charging the drum and exposing the charged drum to the light corresponding to the information of image on a given document, convert the electrostatic latent image into a toner image, i.e. a visible image, by deposition of toner particles thereon, and transfer this toner image onto a copying paper.
The image forming apparatuses of this kind are extensively utilized for copying information in virtually every field of the industry. The apparatus possessing an ability to inscribe such additive image data as date and page number on a copying paper in addition to an ability to reproduce the image of a given document has been developed.
It is when the date on which the reproduction of an image on a given document is actually used in the reproduction of a given image is desired to be preserved for subsequent reference that the data of the date is additionally inscribed on the copying paper by the use of the image forming apparatus endowed with this ability. Generally, the date to be recorded on a reproduced copy, when the reproduced copy happens to contain data for a meeting, is that on which the meeting is to be actually held. Not infrequently, this date differs from the date on which the reproduced copy is produced, namely the copying paper is actually used for the reproduction of the data.
The inscription of the data of a date has been heretofore effected by reading the date to be inscribed on a clock IC incorporated in the image forming apparatus and, on the basis of the data of the read date, driving a device for executing the inscription such as, for example, a LED array head composed of a multiplicity of LED elements and adapted to control the switching of individual LED elements in conformity with the information to be inscribed, a laser device adapted to control the switching of a laser beam in conformity with the data to be inscribed, or a liquid crystal shutter head thereby forming a desired additional image.
By the use of the conventional image forming apparatus endowed with an ability to inscribe the data of a date, however, since the date read from the clock IC is present date, the date on which the image is reproduced is inscribed on the copying paper. Where the date concurrent with the date of actual use of the reproduced copy is desired to be inscribed as described above, therefore, the reproduced copy must be produced on the date on which it is put to use. The ability of the image forming apparatus to inscribe a date is not fully utilized because the reproduced copy is not allowed by this image forming apparatus to be produced on a date different from the date on which the reproduced copy is actually used.